Healthy eating programmes in schools could backfire and merely encourage children to eat more junk food out of school hours, an expert has said.

The warning comes as a primary school in Surrey was accused of banning crisps and chocolate bars from pupils' lunchboxes.

Newspaper reports claimed "food fascists" at Broadmere Community Primary in Sheerwater were threatening to confiscate unhealthy ingredients in packed lunches.

We are not going to fall out with anyone over packed lunches

David Holcombe, Broadmere Community Primary

BBC News Online understands no teacher or supervisor at the school has the authority to take food off children.

Rather the idea is to support parents in getting children to eat a more nutritious diet.

But the head teacher, David Holcombe, has admitted the drive to get pupils to bring in more healthy packed lunches prompted concern from some parents.

"When we realised that some parents were concerned, we immediately sent out another newsletter welcoming the debate," said Mr Holcombe.

"We are not trying to usurp your role as parents. In other words we are not going to fall out with anyone over packed lunches."

A spokesman for Surrey County Council said: "With hindsight, the message to parents did not come across in the way in which it was intended."

Wrong approach

The school is taking part in the government's healthy schools programme, set up in 1998 by the Department for Education and the Department of Health.

Topics such as road safety, personal hygiene and healthy eating are covered.

Health professionals are worried about the rise in overweight children

But Dr Dee Dawson, medical director of the Rhodes Farm Clinic for Eating Disorders, said trying to discourage children from eating "naughty" foods such as crisps and chocolate may just make them eat more.

"You're not going to convince children they don't like crisps and chocolate by giving them carrots - we all like crisps and chocolate," said Dr Dawson.

"There's no evidence that you can wean children off eating crisps and chocolate because you don't let them take them to school.

"In fact I'm sure there'll be evidence that shows that children are going to rush home and eat more if you try and restrict them," she warned.

Obesity fears

Dr Dawson said growing fears about the number of overweight children was more a question of exercise than of diet.

"Research shows that children actually don't eat any differently from the way they did 20 or 30 years ago when there was slightly less obesity.

"The difference is that they're not taking any exercise now, they're not playing in the street , they're not riding their bicycles, not walking to school - they're sitting, playing computer games and being driven."

Dr Dawson said children should eat three good meals a day, including some protein, fruit and vegetables.

"Now once you've given children their share of vegetables and fruit and protein, it doesn't really matter how they fill up on the extra calories that they need for energy... but they're certainly not going to get enough energy from carrot sticks."